HR: 0800h
AN: H31C-1317    [Abstracts]
TI: Geochemical Analysis of Recharge and Groundwater Salinization in the Northern Hueco Bolson Aquifer, El Paso County, Texas
AU: * Druhan, J L
EM: jenny@hwr.arizona.edu
AF: SAHRA, University of Arizona Marshall Building 845 N. Park, 5th Floor, Tucson, AZ 85721-0158 United States
AU: * Druhan, J L
EM: jenny@hwr.arizona.edu
AF: University of Arizona Department of Hydrology and Water Resources, John W. Harshbarger Bldg. 1133 E. James E. Rogers Way, Tucson, AZ 85721 United States
AU: Hogan, J F
EM: jhogan@hwr.arizona.edu
AF: SAHRA, University of Arizona Marshall Building 845 N. Park, 5th Floor, Tucson, AZ 85721-0158 United States
AU: Hogan, J F
EM: jhogan@hwr.arizona.edu
AF: University of Arizona Department of Hydrology and Water Resources, John W. Harshbarger Bldg. 1133 E. James E. Rogers Way, Tucson, AZ 85721 United States
AU: Eastoe, C
EM: eastoe@geo.arizona.edu
AF: SAHRA, University of Arizona Marshall Building 845 N. Park, 5th Floor, Tucson, AZ 85721-0158 United States
AU: Eastoe, C
EM: eastoe@geo.arizona.edu
AF: University of Arizona Department of Geosciences, Gould-Simpson Building, 208 PO Box 210077, Tucson, AZ 85721 United States
AU: Hibbs, B J
EM: bhibbs@calstatela.edu
AF: CEA-CREST, California State University, Los Angeles Biological Sciences BS140, Los Angeles, CA 90032 United States
AU: Hibbs, B J
EM: bhibbs@calstatela.edu
AF: California State Univeristy, Los Angeles Department of Geological Sciences, Geological Sciences PS 2156, Los Angeles, CA 90032 United States
AU: Hutchison, W R
EM: bhutchison@epwu.org
AF: El Paso Water Utility, P.O. Box 511, El Paso, TX 79961 United States
AB: The Hueco Bolson aquifer is a principal water resource for the cities of El Paso and Ju rez. Identification of the primary groundwater recharge zones and the distribution and dynamics of salinity are needed in order to understand the impact of historic and current pumping of freshwater resources and future development of a desalination plant to utilize brackish groundwater resources. Historic pumping has resulted in a persistent increase in the salinity of freshwater resources, forcing the El Paso Water Utilities (EPWU) to abandon several once highly productive wells. The mechanisms for this pumping induced salinization may include lateral migration from elsewhere in the basin, leakage from mud and clay layers and upward movement of deeper brackish to saline groundwater. Isotopic and chemical analysis of groundwater from recently constructed test holes and wells with multiple discrete vertical zone samples has provided a unique opportunity to characterize recharge waters and salinity sources, and to identify the primary mechanisms of pumping induced salinization. O and H isotopes were used to delineate two distinct recharge zones in the northern portion of the aquifer. The western zone along the Franklin Mountains, where the lowest salinity levels are observed, exhibits linear trends of decreasing δ¹⁸O and δD with depth and little evidence of evaporation. This observation is consistent with southeastern movement of Tularosa groundwater beneath shallow mountain front water from the Franklins, recharging the fluvial deposits of the ancestral Rio Grande which flank the mountain front, and flowing south along the axis of the deposits. The central zone shows a different isotope stratigraphy, with both shallow and deep evaporated waters separated by a layer of less evaporated, isotopically lighter water at intermediate depth. This may suggests direct infiltration of evaporated waters on the surface, as well as a deep section composed of ancient lacustrine waters, whereas the intermediate layer may result from continued southeastern movement of deep waters from the western zone. Incorporation of anion ratios and S isotope data with the O and H isotopes indicates upwelling of deep saline brines as the primary source of salinization in the central portion of the aquifer. Anion mixing trends of this highly saline deep water (>15,800 mg/L TDS) with a dilute, slightly evaporated meteoric water accounts for the majority of data throughout the study area. Several secondary salinity sources appear to affect specific locations, including areas of localized halite dissolution, leakage from mud or clay layers and an undetermined surface source of bromide in several central zone wells. Ultimately, this understanding of recharge and salinity sources will be incorporated into an updated version of a groundwater flow and transport model for the Hueco Bolson, which will aid in further developing and refining strategies of groundwater resource management.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: Fall Meeting 2005